Compound diesel engine of rotary-piston type

ABSTRACT

A compound internal-combustion engine of rotary-piston type having two sets of juxtaposed rotary-piston engine units each including a housing with a bilobed epitrochoidal or approximately epitrocoidal inner surface and a substantially triangular shaped rotor rotatably mounted on an eccentric portion of a shaft journaled in said housing with the apexes thereof adapted to be moved in sliding contact with the inner surface of the housing. One of the engine units works as an internal-combustion engine and the other unit serves as a compressor. The shaft of the second unit runs in the same direction as that of the first unit but at twice the speed, and a rotary control valve is installed between the two units so that air compressed in the second unit is supplied syncronously to the rotation of the first unit.

fay 15, 1973 ilnite States Patent [191 Tado et all.

[541 COMPOUND DIESEL ENGINE 0F ROTARY-PISTON TYPE PrimaryExaminer-Carlton R. Croyle Assistant ExaminerMichael Koczo, Jr.Attorney- Stevens, Doris. Miller & Mosher [75] Inventors: Hiroshi Tado,Suita; Teruo Morimoto, Nagahama, both of Japan ABSTRACT [73] Assignee:Yanmar Diesel Engine Co., Ltd.,

Osaka, Japan A compound internal-combustion engine of rota piston typehaving two sets ofjuxtaposed rotary-piston engine units each including ahousing with a bilobed epitrochoidal or approximatel 22 Filed: May24,1971

Appl. No.: 146,028

y epitrocoldal inner surce and a substantially triangular sha rtfr m wmh m mm fl e d h m a mu .l W na 0 p6 U S Cl 123/805 rotatably mounted onan eccentric 51 lm. CI..........................F02b 41/02, F02b 53/08journaled in Said housing with m [58] Field OfSearch..................l23/8.43, 8.29, 8.41, da ted to be moved insliding ontact 1 /8- 119 6O/15, 39-43 surface of the housing. One of theengine units works as an internal-combustion engine and the other unitserves as a compressor. The shaft of the second unit runs in the samedirection as that of the first unit but at twice the speed, and a rotarycontrol valve is installed between the two units so that air com thesecond unit is supplied syncronousl tion of the first unit.

[5 6] References Cited pressed in y to the rota- 1 Claim, 14 DrawingFigures 7 III IIIIi I'll PATENTED 51975 3. 732 689 sum 1 0r 5 ATTORNEY!PATENIEUNAYWBB 3,732,689

SHEET 2 [IF 5 PATENTED 3,732,689

SHEET 5 OF 5 COMPOUND DIESEL ENGINE OF ROTARY-PISTON TYPE This inventionrelates to a rotary-piston engine, and more specifically to theconstruction of so-called orbiting rotary-piston engine.

A rotary-piston engine of the construction above re ferred to usuallyuses a substantially multisided rotor (to be hereinafter called a rotor)which is mounted offcenter on the output shaft of the engine and held ina housing having a multilobed, or more commonly a bilobed, epitrochoidalinner geometry, and which rotates with its apexes in continuous slidingcontact with the curved inner surface of the housing. In an engine ofthis type wherein given spaces are provided as working chambers betweenthe inner surface of the housing and the flanks of the rotor, the volumeof the working chamber in which the rotor as a rotary piston is at itstop dead center for maximum compression of the charge is very large ascompared with the volume in a reciprocating-piston engine, and it isdifficult to attain a desirable compression ratio of the charge.

In an effort to eliminate the foregoing disadvantage, it has beenproposed to juxtapose a pair of rotarypiston engine units of the samedesign and cause them to run in the same direction at the same speed, insuch a manner that one of the engine units serves as a compressor andsupplies compressed air to the intake port of the other engine unit and,at the same time, the exhaust from the engine unit is returned to thecompression unit for reexpansion so that the compressor unit plays therole of a rear-stage expansion unit, too. Engines of the constructiondescribed, known as compound internal-combustion engines ofrotary-piston type, have been known in the art from the publishedspecifications of Japanese Patent Publication Nos. l2554/1964, 681/1965,11922/1966 and 11321/1969.

The ratio of the stroke volume of the engine unit (hereinafter calledthe first unit) to that of the compressor unit (hereinafter called thesecond unit) is usually l 2 or upwards where the Diesel cycle isemployed. This is because a volume ratio between 1 2 and 1 3 isnecessary in order to attain a sufficient compression ratio for a properDiesel cycle and provide a desired space where a good combustionefficiency is attained in the maximum compression state with the rotorof the first unit at its top dead center.

If the stroke volume ratio of the first and second units is 1 2, itmeans that, provided that the both units have epitrochoidal housings ofthe same profile (hereinafter called the rotor housings), the width ofthe rotor housing for the second unit must be twice as large as that ofthe first unit. If the both rotor housings of the first and second unitsare to have the same width, then the epitrochoidal profile of the secondunit will have to be much larger than that of the first unit. Whichevermethod may be resorted to, the second unit has to be bulkier than thefirst unit, thus necessitating a large overall construction and anincrease in weight as inevitable shortcomings.

The present invention is proposed to eradicate those shortcomings of thecompound engines above described. It enables the rotor of the secondunit of such an engine to run in the same direction as that of the firstunit but twice as fast as the latter so that the first unit in itsintake stroke can take in a volume of air about twice as large as thestroke volume of the second unit.

In this manner working spaces are secured which render it possible toexpect adequate combustion of the charge in the Diesel cycle whilerestricting any increase of the overall dimensions of the structure andminimizing its weight gain.

The invention will be more fully described hereunder in conjunction withthe accompanying drawings showing an embodiment thereof. In thedrawings:

FIG. 1 is a sectional view taken along the line BB of FIG. 2illustrating an embodiment of the invention;

FIG. 2 is a sectional view taken along the line A-A of FIG. 1; and

FIGS. 3 through 14 are views explanatory of the rotatory positions whichare assumed at sequential moments by a pair of rotors accommodated in anengine according to this invention.

Referring to FIGS. 1 and 2, a rotor housing common to the first andsecond units is generally indicated at 1, and there are shown a pair ofrotors 3, 5 and output shafts 7, 9 which have eccentric portions 7a, 9a,respectively. In a side housing 15 are secured gears 1 1, 13, which arein mesh with inner gears 17, 19 mounted, respectively, on the rotors 3,5, the gear ratio being 2 z 3. To one ends of the shafts 7, 9 are fixedgears 21, 23, which are in communication with each other through anintermediate gear 25. The gear ratio of the gear 21 mounted on the firstunit and the gear 23 on the second gear is 2 l, the shaft 9 of thesecond unit makes two revolutions while the shaft 7 of the first unitcompletes one revolution. FIG. 1 shows a fresh-air intake port 27, afresh-air supply port 29 through which the fresh-air from the port 27 issupplied to the first unit, and a fresh-air filling port 30 for thefirst unit. A rotary control valve 31 is formed with a passageway 33.The rotating motion of the control valve is transmitted by means of aserrated belt 39 which is engaged with a pulley 37 fixedly mounted onthe shaft 7 of the first unit and a pulley 35 on the shaft end of thecontrol valve 31. Thus, the valve 31 is driven in the same direction andat the same speed as the shaft 7 of the first unit, and the rotation ofthe valve 31 is synchronized with that of the shaft 7 of the first unitso that the passageway 33 continuously changes the cross sectional areaof the fresh air passage between the fresh-air supply port 29 andfilling port 30 and, at certain intervals, shuts off the passage betweenthe two ports. Numeral 41 indicates a hot-gas discharge port, 43 ahot-gas inlet port communicated with the discharge port via a passage,45 an exhaust port for waste gases, and 417 a fuel injection valve.Arrow marks show the revolving direction of the engine.

Next, the operation of the engine according to the present inventionwill be explained with reference to FIGS. 3 to 14. Throughout thesefigures, the unit at left is the second unit and the one at right is thefirst unit, and arrow marks indicate the revolving direction. Forconvenience of illustration, the operation in connection with only thechamber V of the first unit will be followed. FIGS. 1 and 3 show theengine in such a positional relationship that one flank of the rotor 5of the second unit is on top of the hot-gas inlet port and one flank ofthe rotor 3 of the first unit on top of the freshair filling port. Herethe rotors of the first and second units and the passageway 33 throughthe control valve 31 are so positioned that the passageway does notcommunicate the fresh-air supply port 29 to the fresh-air filling port30. In this state intake of fresh air into the chamber V is yet to bestarted. FIG. 4 shows the passageway 33 of the control valve 31 about toestablish a communication between the fresh-air supply port 29 and thefilling port 30. At this time, one of the apexes of the rotor 5 of thesecond unit is at a point past the fresh-air supply port. In FIG. 5,fresh air taken in through the intake port 27 of the second unit is ledthrough the passageway 33 of the control valve 31 into the chamber V, ofthe first unit. The intake from the fresh-air intake port 27 into thechamber V, of the second unit has been completed. In continuation fromthe state shown in FIG. 5, the volume of the chamber V of the first unitkeeps on expanding with the decrease in the volume of the chamber V ofthe first unit as shown in FIG. 6, so that the chamber V is continuouslycharged with fresh air via the passageway 33 through the control valve31. At this point the cross sectional area of the passage through thepassageway 33 of the control valve 31 approaches a maximum value.Meanwhile, the chamber V of the second unit begins intake and, with theexpansion of the chamber V the intake progresses throughout theconditions illustrated in FIGS. 7 to 9. FIG. 9 shows the chamber V ofthe second unit in its minimum volume and the passageway 33 through thecontrol valve 31 closed out of communication with the fresh-air fillingport 30, thus completing the supply of fresh air from the chamber V ofthe second unit into the chamber V of the first unit. During the processfrom FIG. 9 to FIG. 10 the chamber V of the first unit shows somepressure drop because the passageway 33 of the control valve 31 remainsclosed against admittance of fresh air and, moreover, the chamber keepson expanding for the limited period of time. However, in a slightlyadvanced state from FIG. 10, one of the apexes of the rotor of thesecond unit passes the freshair supply port 29 and begins to open thepassageway 33 of the control valve 31. For some time during the progressfrom FIG. 10 to FIG. 11 the passageway 33 of the control valve 31 isopen and the fresh-air intake port 27 of the second unit also remainsopen. Fresh air admitted into the chamber V of the first unit duringthis period then flows into the chamber V of the second unit and tendsto flow back to the outside through the fresh-air intake port 27. Thisperiod is extremely short, however, and the amount of air that flows outof the intake port 27 is negligibly small. FIGS. 11 to 14 illustrate howthe chamber V of the first unit is increasingly supercharged with airfrom the chamber V of the second unit. In FIG. 14 the intake in thechamber V is over and compression starts in the same chamber. Thus,because the shaft 9 of the second unit makes two revolutions while theshaft 7 of the first unit completes one revolution, it follows that ifthe stroke volume of the second unit is equal to that of the first unit,the first unit will be charged with approximately twice as much air asthe stroke volume of the first unit. With the engine of the constructionso far described, it is possible effectively to realize a Diesel cycleby choosing an appropriate volume ratio without materially increasingthe stroke volume of the second unit as compared with that of the firstunit. It should be clear to those skilled in the art that the presentinvention which permits reduction in size of the second unit willprovide a small-size, compact and lightweight engine. Also, as will beappreciated from the foregoing description, the high pressure gasesafter combustion in the first unit are led into the two chambers of thesecond unit where the gas energy is recovered therefrom. Therefore, ascompared in the conventional arrangement wherein the rotors of the firstand second units are driven in the same rotational speed, the rotor 5 ofthe second unit according to this invention requires no specialconsideration for cooling; it may be simply an air-cooled rotor. This isanother advantage of the invention, though of secondary importance.

The foregoing description has been made on the assumption as alreadystated at the beginning of the explanation of the operation that, whenthe positional relationship is such that one flank of the rotor of thesecond unit is above the top end of the hot-gas inlet port and one flankof the rotor of the first unit is above the top end of the fresh-airfilling port, then the rotors of the first and second units and thepassageway of the control valve are so positioned with respect to oneanother that the passageway of the control valve is closed to shut offthe communication between the fresh-air supply port and filling port. Itis also possible, of course, that one flank of the rotor of the firstunit may come to the front or back of the top end of the fresh-airfilling port. If such is the case, it is needless to say that thesynchronized action of the control valve with the rotation of the shaftof the first unit will have to be accordingly modified and set to aproper value. Driving of the control valve may be accomplished by eithershaft end of the first or second unit. If the control valve is to bedriven by the output shaft of the second unit, it is only necessary tochoose a speed ratio of l 2 for the valve and the shaft of the secondunit. As for the driving means, gear and chain-drive systems may beemployed as well without departing from the spirit and scope of thepresent invention. The arrangement shown in FIG. 2 is merelyillustrative of the principle of the invention.

What is claimed is:

1. A compound diesel engine of the rotary piston type, consisting of twosets of juxtaposed rotary-piston engine units each including a housingwith a bilobed epitrochoidal or approximately epitrochoidal innersurface and a substantially triangular shaped rotor rotatably mounted onan eccentric portion of a shaft journaled in said housing with theapexes thereof adapted to be moved in sliding contact with the innersurface of the housing, one of the engine units working as aninternal-combustion engine and the other serving as a compressor,

a filling passage connecting a fresh-air filling port of said internalcombustion engine with a fresh-air supply port of said compressor,

a return passage connecting a combustion gas discharge port of saidinternal combustion engine with a combustion gas inlet port of saidcompressor,

characterized in that the shaft of said compressor rotates in the samedirection as that of the internal combustion engine but at twice thespeed of said internal combustion engine, and

a rotary control valve installed in said filling passage, said valvebeing synchronized with one of said shafts such that said rotary slidevalve begins to open when one apex of the rotor of the compressor movespast the fresh-air supply port and closes when the rotor of thecompressor is at the intersection dead center with respect to thefresh-air supply port and the combustion gas inlet port whereby in onesuction stroke of the internal combustion engine, a volume of aircorresponding two times of suction and compression strokes of thecompressor is filled in the working chamber of the internal combustionengine pertaining to such suction stroke.

1. A compound diesel engine of the rotary piston type, consisting of twosets of juxtaposed rotary-piston engine units each including a housingwith a bilobed epitrochoidal or approximately epitrochoidal innersurface and a substantially triangular shaped rotor rotatably mounted onan eccentric portion of a shaft journaled in said housing with theapexes thereof adapted to be moved in sliding contact with the innersurface of the housing, one of the engine units working as aninternalcombustion engine and the other serving as a compressor, afilling passage connecting a fresh-air filling port of said internalcombustion engine with a fresh-air supply port of said compressor, areturn passage connecting a combustion gas discharge port of saidinternal combustion engine with a combustion gas inlet port of saidcompressor, characterized in that the shaft of said compressor rotatesin the same direction as that of the internal combustion engine but attwice the speed of said internal combustion engine, and a rotary controlvalve installed in said filling passage, said valve being synchronizedwith one of said shafts such that said rotary slide valve begins to openwhen one apex of the rotor of the compressor moves past the fresh-airsupply port and closes when the rotor of the compressor is at theintersection dead center with respect to the fresh-air supply port andthe combustion gas inlet port whereby in one suction stroke of theinternal combustion engine, a volume of air corresponding two times ofsuction and compression strokes of the compressor is filled in theworking chamber of the internal combustion engine pertaining to suchsuction stroke.